1. Pathways for North American Outflow - Hindcast for ICART2
Qinbin Li, Daniel J. Jacob, Rokjin Park, Colette L. Heald, Yuxuan Wang, Rynda Hudman, Robert M. Yantosca
Harvard University
Mian Chin
NASA/GSFC
with support from NOAA Atmospheric Chemistry Program
Hindcast for ICARTT, summer INTEX-NA, ITCT-2K4, ITOP etc.; the questions we ask: 1. what are the pathways for NA pollution outflow? 2. what chemical evolutions occur in the different outflow processes? 3. What can we learn from satellite observations on pollution outflow? 4. Any interannual variabilities in the outflow, for example, influence from El Nino on circulation? 5. Contributions from other continents to the NA outflow?
ICART2 Planning Meeting, 1/21/2004
NOAA Aeronomy Lab, Boulder, CO

2. Model Simulations GEOS-CHEM Model Simulations Observations
Global 3-D model of tropospheric chemistry-aerosols.
Driven by GMAO GEOS-3 assimilated meteorology.
Used in TRACE-P and ITCT-2K2 chemical hindcasts / forecasts
and post-mission analyses.
Model Simulations
Time period: June-August of 1998, 2000, 2001, 2002
Tagged CO (all four years): 2°x2.5° (use 1998 FF and climatological
BB emissions for all four years)
Full-chemistry (2000 only): 1°x1° ‘nested’ over North America
(use 2000 BB emissions)
Observations
MOPITT CO column
MODIS aerosol optical depth
AERONET aerosol optical depth
Don’t want to bore you with details of the model; assimilated meteorology allows simulation of interannual variabilities and specific events; focus on summer; first general patterns of the outflow and any interannual variabilities; 1998-El Nino; 2004-latest observed SST trends and model forecasts indicate “neutral” to weak El Nino; focus on summer 2000, analysis of MOPITT CO column, MODIS and AERONET AOD.

3. Summer 2004: El Niño, La Niña, or Neutral?
The most recent Niño 3.4 SST anomalies fall in the range of near-neutral conditions.
Most of the statistical and dynamical model forecasts are indicating slightly above-average conditions over the coming several months.
As we will show, El Nino could have impact on NA outflow. El Nino and La Niña episodes typically last approximately 9-12 months. They often begin to form during June-August, reach peak strength during December-April, and then decay during May-July of the next year.

4. GEOS hPa Winds, 2000 H H
Zonally-uniform flow pattern in June, while curve-like flow patterns in July and August.
The circulation; a contrast between 2000 (close to “neutral”) v.s (El Nino). Southward shift of jet stream in June 1998; H H

5. GEOS hPa Winds, 1998 H H
El Nino influence lasted into June; outflow in June at lower latitudes than other years. H H

6. GEOS-3 500 & 300 hPa Winds 300 hPa H 500 hPa H
Recirculation in the middle and upper troposphere.
300 hPa H
Recirculation in the middle to upper troposphere.
500 hPa H
Recirculation in the middle to upper troposphere. We’ll come back to this.

7. North American Emissions
Duncan et al. [2003]
unit: molec/cm2/s FF
BB, June
BB, July
BB, August
Climatology
BB, July
2000
BB, August
2000: huge forest fires in NW (Montana, Idaho, Wyoming, etc.)
Boreal forest fires v.s. unusually large forest fires in NW U.S. in July and particularly August 2000.
Climatology: extensive boreal forest fires.

8. Horizontal N. American CO Flux, June
2000
Different latitudes in BB v.s. FF outflow. Lower latitudes outflow in June 1998.
1998
FF outflow at 35ºN-50ºN, BB outflow 45ºN-55ºN.
Outflow at much lower latitudes in June 1998.

9. Horizontal N. American CO Flux, 2000
July
Lower latitudes outflow in July than in June and August because of the subtropical troughs.
August
Outflow in July is at lower latitudes than in June.
Outflow in August shows features in between June and July.

10. Vertical and Zonal N. American CO Flux, June
2000
1998
70ºW
300 hPa
70ºW
70ºW
Lines – fluxes (vertical: moles cm-2 s
zonal: moles cm-2 s)
Color contours – concentrations (ppb)
(1) BL and lower FT outflow.
(2) Convective outflow in MT/UT.

11. Vertical and Zonal N. American CO Flux, July
70ºW
300 hPa
70ºW
70ºW
Lines – fluxes (vertical: moles cm-2 s
zonal: moles cm-2 s)
Color contours – concentrations (ppb)
Stronger convective transport than June and August.

12. Vertical and Zonal N. American CO Flux, August
70ºW
300 hPa
70ºW
70ºW
Lines – fluxes (vertical: moles cm-2 s
zonal: moles cm-2 s)
Color contours – concentrations (ppb)

13. Event June 9-13: BL, WCB and Convective Outflow
GOES IR
AERONET

14. Event June 9-13: WCB, Convection
from Midwest
from southeast

15. Event July 2-7: Outflow at Low Latitude
Mopitt only July 2-3, no data for July 4-14; what is the freq of MOPITT, MODIS? Ask wife
GOES IR
AERONET

16. Event July 2-7: Outflow at Low Latitude
Enhanced CO.
Enhanced ozone and aerosols.

17. Recirculation in the Upper Troposphere North American Fossil Fuel CO
270 hPa, July 6-23, 2000
Deep convection in the south-central U.S. followed by recirculation in the MT and UT; fairly aged air masses with high ozone but depleted NOy and aerosols upon leaving the continental U.S.
(animation)

18. Event July 9-14: Recirculation
AERONET
GOES IR

19. Event July 9-14: Recirculation
Enhanced CO in the upper troposphere.
Enhanced ozone in the upper troposphere.
Aerosols are depleted.

20. Asian and European Influences Detectable?
Asian and European influences dispersed into the background.
Asian plumes could be seen in strong transpacific transport.
> 40 ppbv

21. N. American Biomass Burning CO, 500 hPa
August 2000
Plumes from the huge fires in the northwest US are lifted to 5-8 km by convection and then exported
(1) northeastward north of 50ºN
(2) eastward by the westerly at 40-50ºN
(3) southeastward at 30-45ºN and impacts much of the middle and east U.S.
(animation)

22. N. American Fossil Fuel CO, 850 hPa
July, 2000

23. N. American Fossil Fuel CO, 500 hPa
July, 2000

24. N. American Fossil Fuel CO, 300 hPa
July, 2000

25. Summary and Conclusions
Main pathways: BL and lower FT outflow; Convective outflow in the MT and UT.
Outflows occur at a rather large latitude range (30ºN-55ºN) along the east coast.
Deep convections in the south-central U.S. are often followed by recirculation in the MT and UT over much of the U.S.
Biomass burning outflows generally occur at higher latitudes (45ºN-55ºN) than anthropogenic outflows.
Outflows occur at lower latitudes in July and August than in June due to more curve-like flow patterns in July and August.
MOPITT CO columns and MODIS and AERONET aerosol optical depths provide useful insights in understanding N. American pollution outflow.